In many electronic systems, small electronic modules containing a printed circuit board (PCB) with packaged semiconductor devices mounted thereon are used to provide some specific type of functionality. The electronic module may facilitate assembly and/or protect the components housed inside. For example, an optical module may have an optical connector for receiving optical signals, where the connector can be configured as a female receptacle for receiving a complementary shaped male plug. Inside, the optical module may devices for converting the optical signal into an electrical signal, as well as logic processing devices and memory for operating upon the electrical signal.
FIG. 1 shows an example optical module of the prior art. Optical module 10 includes an optical connector 12 in the form of a female receptacle, and is composed of a top enclosure 14 and a bottom enclosure 16. The use of terms “top” and “bottom” are arbitrary, and specifically refer to the relative position of the enclosure portions shown in FIG. 1. Electronic modules such as optical module 10 of FIG. 1 can be referred to as SFP (Small Form-Factor Pluggable) or QSFP (Quad SFP) enclosures. Regardless the type of enclosure, they are intended to have the smallest possible form factor.
Unfortunately, the packaged devices within the electronic module generate heat during normal operation. By example, the electronic module can contain package on package (POP) devices, which are a widely used packaging technology to three dimensionally integrate multiple functions into a single form factor. In the vast majority of cases, the POP stack comprises a logic processor chip onto which a DRAM package is placed on top. Both devices of the POP stack generate heat during the normal course of operation. This generation of heat by both devices of the POP stack is undesired as excessive heat can cause both devices to fail. The primary failure mechanism due to excessive heat is thermal runaway, where heat increases the amount of leakage current from the circuits, which then creates additional device power to increase the heat output. This problem loops continuously until catastrophic failure occurs, or the device simply fails to operate properly any further.
In an optical module such as an SFP, the volume constraints of the form factor do not allow many options for removing heat from the internal devices as proper cooling involves physically moving heat as far from the thermal source as possible. Optical modules have very stringent thermal specifications and require operation in ambient temperatures of up to 70 C. In the best of cases, cooling of a POP in the optical module is challenging, and for integration into an optical module, a novel cooling method to allow reliable operation is required.
It is therefore desirable to remove heat from the internal devices and into the surrounding environment without introducing additional power consuming components into the system.